The San José Semaphore

Embedded into the façade of a tall office building in downtown San José, four digital yellow circles rotate every few seconds, seemingly without purpose. This display has gone on since 2006, and it could be easily dismissed as an unusual artistic choice by the resident of the building, the software company Adobe. But in actuality, this light installation, the San José Semaphore, is beaming a code across the city.

The artist, Ben Rubin, replaces the code each time it's cracked, which so far has happened twice. The first time, two tech workers attending a downtown seminar on how to flirt with girls spotted the Semaphore and spent the next several months breaking down the code. In the summer of 2007, they announced that hidden beneath references to James Joyce's Ulysses and the Vigenère cipher was the entire text of Thomas Pynchon's novel The Crying of Lot 49. 

The second time, in 2017, a Tennessee math professor cracked the next code, discovering that the circles had been transmitting an audio recording of the first moon landing. A new code started transmission at the top of Adobe’s Almaden Tower on May 11, 2023.